Usually in my experience people on the phone like this tend to raise their voice more than people in a normal conversation would, or even using the phone normally (same goes for people talking through earbuds or wireless ear pieces). I also see more people who are talking on the phone like this not paying attention to their surroundings because they are already doing 2 things that require attention, and so they tend to be inconsiderate about others. Of course it isn't everyone that ever does this, but really it is just the ones that show complete disdain for anyone around them since they are caught up in their own little world. Happens enough to be annoying, but even that one guy in the airport wandering around yelling into his phone/earbud, cutting people off who are trying to get somewhere, is annoying enough.
